JP2018077351A - Electrophotographic photoreceptor and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor that can reduce image defects for a long period and ensure cleanability at the initial stage of use, and an image forming apparatus including the same.SOLUTION: An electrophotographic photoreceptor comprises: a substrate; and a photosensitive layer formed on the surface of the substrate. When the arithmetic average roughness of the surface of the photosensitive layer at the initial stage of use is Ra, and the average distance between projections and recesses on the surface of the photosensitive layer in the circumferential direction and axial direction of the substrate is Sm1 and Sm2, respectively, Ra≤100[nm] and Sm1<Sm2 are satisfied.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrophotographic photosensitive member on which a toner image is formed and an image forming apparatus including the electrophotographic photosensitive member.

  In an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine having these functions, a photosensitive drum that is an example of an electrophotographic photosensitive member, a charging device that charges the surface of the photosensitive drum, and a photosensitive member There is known a cleaning blade that is disposed in contact with the drum surface and has a cleaning blade that removes toner and external additives remaining on the surface of the photosensitive drum.

  The photosensitive drum is composed of, for example, a metal base tube that is a support and a photosensitive layer formed on the surface of the base tube. As the photosensitive drum, for example, an amorphous silicon photosensitive member in which amorphous silicon is laminated as a photosensitive layer is widely used.

  This amorphous silicon photoreceptor has minute irregularities formed on the surface by crystal grain boundaries. In an image forming apparatus using an amorphous silicon photoconductor, unevenness present on the surface of the photoconductor drum in the initial stage of use is polished and smoothed by long-term use. Therefore, the contact area between the photosensitive drum and the cleaning blade increases, and the friction coefficient increases. As a result, the rotational torque of the photosensitive drum rises, and the cleaning blade is worn or lost due to an increased load on the cleaning blade. When the cleaning blade is worn out or lost, the toner external additive slips out, leading to contamination of the charging roller in contact with the photosensitive drum and charging failure resulting therefrom. Further, since the adhesion of the toner and the toner external additive is increased in the smoothed photosensitive drum, there is a problem that a good cleaning property cannot be obtained.

  Therefore, as shown in Patent Document 1, a method for roughening the surface of the photosensitive drum has been proposed in order to reduce the contact area between the photosensitive drum and the cleaning blade or toner. In the photoreceptor drum described in Patent Document 1, irregularities are formed by a plurality of spherical trace depressions on the surface of the raw tube, and the 10-point average roughness Rz at the 2.5 mm reference length of the surface of the photoreceptor drum is 0.72 [ [mu] m] or more and 1.25 [[mu] m] or less. This suppresses toner adhesion during residual toner cleaning and improves the scratch resistance of the surface of the photosensitive drum.

Japanese Patent Laid-Open No. 11-143099

  However, when the unevenness is defined only by Rz as in Patent Document 1, if Rz is simply increased to reduce the contact area between the photosensitive drum and the cleaning blade, the distance between the uneven peaks and valleys is increased, and the valley portions are separated. Some parts are difficult to clean. For this reason, in the initial stage of use of the photosensitive drum, the external additive and the like slipping through the concave and convex valleys increase. That is, in the conventional configuration, the design of the surface roughness (unevenness) that suppresses the cleaning failure in the initial use of the photoconductor drum and the design of the surface roughness (unevenness) for extending the life of the photoconductor drum are compatible. It was difficult.

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an electrophotographic photosensitive member capable of suppressing image defects over a long period of time and ensuring cleanability in the initial use and an image forming apparatus including the same.

  In order to achieve the above object, a first configuration of the present invention is an electrophotographic photosensitive member having a support and a photosensitive layer formed on the surface of the support. The electrophotographic photosensitive member has a large number of elongated protrusions extending in the axial direction of the support on the surface of the photosensitive layer in the initial stage of use, and Ra represents the arithmetic average roughness of the surface of the photosensitive layer in the initial stage of use as Ra. When the average intervals between the concave and convex portions in the direction and the circumferential direction are Sm1 and Sm2, respectively, Ra ≦ 100 [nm] and Sm1 ≦ Sm2 are satisfied.

  The “arithmetic average roughness Ra” and “average interval Sm” in this specification are based on the surface roughness defined in 1994 edition of JISB0601.

  According to the first configuration of the present invention, it is preferable that an external additive of toner or the like does not slip through a gap with the cleaning blade in the initial use of the electrophotographic photosensitive member, and a rotational torque does not increase due to contact with the cleaning blade. The electrophotographic photosensitive member has a surface state and can suppress the occurrence of image defects over a long period of time.

A schematic cross-sectional view showing a schematic configuration of an image forming apparatus 11 on which the photosensitive drum 20 of the present invention is mounted. Schematic showing a configuration around the photosensitive drum 20 of the image forming apparatus 11 Schematic diagram showing a ridge line when the surface of the photosensitive layer 20b of the photosensitive drum 20 according to the embodiment of the present invention is viewed from the axial direction. The schematic diagram which shows the ridgeline when the surface of the photosensitive layer 20b of the photosensitive drum 20 of this embodiment is seen from the circumferential direction. Conceptual diagram showing an actual contact portion between the photosensitive drum 20 and the cleaning blade 52 of the present embodiment in which Sm1 <Sm2. Conceptual diagram showing a contact portion between the conventional photosensitive drum 20 and the cleaning blade 52 where Sm1 = Sm2. Schematic diagram showing how the external additive G stays at the contact portion between the photosensitive drum 20 and the cleaning blade 52. Schematic diagram showing how irregularities are created in the raw tube 20a by bite processing FIG. 8 is a view showing a trajectory when the cutting tool 70 reciprocates once on the raw tube 20a.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus 11 on which a photosensitive drum 20 of the present invention is mounted. FIG. 2 is a schematic diagram showing a configuration around the photosensitive drum 20 of the image forming apparatus 11 shown in FIG.

1. Configuration of image forming apparatus 11 (overall configuration)
As shown in FIG. 1, the image forming apparatus 11 according to the present embodiment is a tandem color printer. The image forming apparatus 11 includes, inside a printer main body 12, a paper feed cassette 13 that stores recording paper (not shown), a paper feeding unit 14 that feeds recording paper one by one from the paper feeding cassette 13, and paper feeding An image forming processing unit 15 that performs an image forming process on the recording paper supplied from the cassette 13 or the manual feed tray (not shown), and a recording paper transport path for transporting the recording paper supplied from the paper feed cassette 13 or the manual feed tray 16, a secondary transfer unit 17 that transfers the toner image formed in the image forming processing unit 15 to the recording paper conveyed along the recording paper conveyance path 16, and the toner image transferred in the secondary transfer unit 17 And a fixing unit 18 that fixes the recording paper.

(Configuration of the image forming processing unit 15)
For example, the image forming processing unit 15 employs a tandem system that performs image forming processing using toner (developer) of four colors of yellow (Y), magenta (M), cyan (C), and black (K). ing. In the following explanation, only in the case of color designation, the symbol of each arithmetic numeral is attached with a color of (Y, M, C, K) in parentheses, and in the common case, only the arithmetic numeral is included. A description will be given with reference numerals.

  The image forming processing unit 15 corresponds to each color (Y, M, C, K) and print data (images) transmitted from a plurality of toner containers 19 containing replenishing toner and an externally connected device such as a personal computer. A plurality of photosensitive drums 20 for forming toner images of respective colors based on the data), a plurality of developing devices 21 for supplying toner to each of the photosensitive drums 20, and a toner image formed on each of the photosensitive drums 20. The endless intermediate transfer belt 22 to which the toner image is primarily transferred, the residual toner attached to the surface of the intermediate transfer belt 22 and disposed upstream of the photosensitive drum 20 on the most upstream side in the rotational movement direction of the intermediate transfer belt 22 A belt cleaning device 24 that removes the light, an exposure unit 25 that emits beam light to each photosensitive drum 20, and a charging device 26 that uniformly charges the surface of each photosensitive drum 20. , And a cleaning device 28 for removing the photosensitive drums 20 residual toner and the like adhering to the surface of the neutralization device 29 for removing the residual charge on the surface of the photosensitive drum 20, a. The photosensitive drum 20 corresponds to an example of the “electrophotographic photosensitive member” of the present invention.

(Configuration of Photosensitive Drum 20)
The photosensitive drum 20 is formed by forming a photosensitive layer on the surface of a support (base). Here, the photosensitive drum 20 includes a metal cylindrical raw tube 20a and a photosensitive layer 20b formed on the surface of the raw tube. The raw tube 20a corresponds to an example of the “support” in the present invention. Examples of the metal forming the raw tube 20a include aluminum, iron, titanium, and magnesium. As the photosensitive layer 20b, an organic photosensitive layer using an organic photoconductor or an inorganic photosensitive layer using an inorganic photoconductor can be used. However, amorphous silicon formed by vapor deposition of silane gas or the like because of its high durability. A photosensitive layer is preferred. Each photosensitive drum 20 carries a toner image of each color on the surface thereof based on the beam light emitted from the exposure unit 25 and transfers the toner image to the intermediate transfer belt 22, as shown in FIG. As described above, the developing device 21 is disposed below the intermediate transfer belt 22.

  As shown in FIGS. 1 and 2, a charging device 26, an exposure unit 25, a developing device 21, a cleaning device 28, and a charge eliminating device 29 are disposed around the photosensitive drum 20, and the intermediate transfer belt 22 is attached to the photosensitive drum 20. The primary transfer roller 27 is disposed opposite to the photosensitive drum 20 with the sandwich.

  The toner image transferred onto the intermediate transfer belt 22 at each primary transfer portion configured by cooperation of the photosensitive drum 20 and the primary transfer roller 27 is recorded from the paper feed cassette 13 or a manual feed tray (not shown). The recording paper conveyed through the paper conveyance path 16 is transferred by the secondary transfer unit 17.

(Configuration of developing device 21)
Each developing device 21 basically has the same configuration and is arranged below the intermediate transfer belt 22 along the rotational movement direction. The developing device 21 includes toner base particles including a binder resin and a colorant, and a toner external additive (hereinafter, also simply referred to as an external additive) composed of metal particles such as titanium oxide attached to the surface of the toner base particles. The electrostatic latent image formed on the surface of the photosensitive drum 20 by attaching a toner containing toner is developed into a toner image. A conventionally known developing device 21 can be used.

(Configuration of the intermediate transfer belt 22)
The intermediate transfer belt 22 is an endless belt that is horizontally stretched between a driving roller and a driven roller in the printer main body 12, and accompanies an image forming operation as the driving roller is rotated by a belt driving motor (not shown). It is circulated and driven.

(Configuration of toner density detection sensor 23)
The toner density detection sensor 23 measures the reflection density of the toner image on the intermediate transfer belt 22 and outputs the detected value to a control unit (not shown). The toner density detection sensors 23 can be provided at a plurality of locations along the rotational movement direction of the intermediate transfer belt 22 and the width direction orthogonal to the rotational movement direction. At this time, if the toner density detection sensor 23 detects the toner density only on one side in the width direction of the intermediate transfer belt 22, for example, a phenomenon in which a density difference occurs on both ends in the width direction of the intermediate transfer belt 22 (single burn phenomenon). It is preferable to dispose near the both ends in the width direction because it is not possible to cope with the occurrence of this.

(Configuration of Charging Device 26)
As shown in FIG. 2, the charging device 26 includes a charging roller 42 that contacts the photosensitive drum 20 and applies a charging bias to the drum surface in the charging housing 41, and a charging cleaning roller for cleaning the charging roller 42. 43.

  The charging roller 42 is formed of, for example, conductive rubber and is disposed so as to contact the photosensitive drum 20. As shown in FIG. 2, when the photosensitive drum 20 rotates in the clockwise direction, the charging roller 42 that contacts the surface of the photosensitive drum 20 is driven to rotate counterclockwise. At this time, the surface of the photosensitive drum 20 is uniformly charged by applying a predetermined voltage to the charging roller 42.

  In addition, as shown in FIG. 2, as the charging roller 42 rotates, the charging cleaning roller 43 that contacts the charging roller 42 is driven to rotate in the clockwise direction to remove foreign matters attached to the surface of the charging roller 42.

(Configuration of the cleaning device 28)
The cleaning device 28 has a cleaning housing 50 having a depth in the recording paper width direction (a direction orthogonal to the recording paper conveyance direction), and is disposed closer to the lower inside of the cleaning housing 50 and rotates clockwise in FIG. A collection spiral 51 that conveys the collected toner to one side in the paper width direction and sends it to a waste toner container (not shown), a cleaning blade 52 attached to the outside lower side of the cleaning housing 50, and an inside upper side of the cleaning housing 50. A rubbing roller (cleaning roller) 53 disposed in contact with the surface of the photosensitive drum 20, and a toner feed guide plate 54 disposed in the cleaning housing 50 between the collecting spiral 51 and the rubbing roller 53. And. A cleaning seal 55 is provided at the upstream end of the cleaning housing 50 in order to prevent the collected toner from leaking from the cleaning housing 50 to the outside.

  The cleaning blade 52 is made of urethane rubber or the like. The cleaning blade 52 is disposed so that the tip abuts against the surface of the photosensitive drum 20 from below the rotation axis of the photosensitive drum 20. At this time, the tip of the cleaning blade 52 abuts in the counter direction with respect to the rotation direction of the photosensitive drum 20 (see the arrow in FIG. 2).

  The rubbing roller 53 collects waste toner from the surface of the photoconductive drum 20 and polishes the surface of the photoconductive drum 20 with the waste toner adhering to the surface of the rubbing roller 53. For this reason, the rubbing roller 53 is formed in a cylindrical shape extending in the recording paper width direction using foamed rubber (for example, carbon-containing conductive foamed EPDM) in order to maintain high retention of waste toner. It is arranged upstream of the front end in the rotational direction of the photosensitive drum 20. Further, the rotation direction of the rubbing roller 53 is opposite to the rotation direction of the photosensitive drum 20.

  The toner feed guide plate 54 divides the side where the rubbing roller 53 exists and the side where the collecting spiral 51 exists, and guides the waste toner collected by the rubbing roller 53 to the collecting spiral 51.

(Configuration of static elimination device 29)
The neutralization device 29 is disposed on the downstream side of the primary transfer roller 27 along the rotation direction of the photosensitive drum 20. As shown in FIG. 2, an LED (light emitting diode) 57 is used for the static eliminator 29, and a reflector is provided as necessary. The static eliminator 29 is attached to the upper surface of the cleaning housing 50 of the cleaning device 28. The static eliminator 29 irradiates the photosensitive drum 20 with static elimination light to remove the charged charges on the surface thereof, and prepares for the charging step in the next image forming operation.

2. Image Forming Procedure Next, an image forming procedure of the image forming apparatus 100 will be described. When image data is input from an externally connected device such as a personal computer, the charging device 26 first uniformly charges the surface of the photosensitive drum 20, and then the exposure unit 25 applies beam light to the surface of the photosensitive drum 20. Irradiation is performed to form an electrostatic latent image corresponding to the image data on each photosensitive drum 20. The developing device 21 is filled with a predetermined amount of a two-component developer (hereinafter, also simply referred to as a developer) containing toner of each color of yellow, magenta, cyan, and black. In addition, when the ratio of the toner in the two-component developer filled in each developing device 21 is less than a predetermined value due to the formation of a toner image described later, the toner is supplied from the toner container 19 to each developing device 21. . The toner in the developer is supplied onto the photosensitive drum 20 by the developing device 21 and electrostatically adheres, whereby a toner image corresponding to the electrostatic latent image formed by exposure from the exposure unit 25 is formed. It is formed.

  On the other hand, the recording paper is fed from the paper feed cassette 13 (or the manual feed tray) in accordance with the toner image formation timing in the image forming processing unit 15, and conveyed to the registration roller pair 30 a through the recording paper conveyance path 16. .

  The primary transfer roller 27 applies an electric field between the primary transfer roller 27 and the photosensitive drum 20 at a predetermined transfer voltage, and yellow, magenta, cyan, and black toner images on the photosensitive drum 20 are transferred to the intermediate transfer belt. 22 is primarily transferred onto 22. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, the toner remaining on the surface of the photosensitive drum 20 after the primary transfer is removed by the cleaning device 28 in preparation for the subsequent formation of a new electrostatic latent image. Further, the residual charge on the surface of the photosensitive drum 20 is removed by the static eliminator 29.

  When the intermediate transfer belt 22 starts to rotate counterclockwise, the recording paper is conveyed from the registration roller pair 30a to the secondary transfer unit 17 provided adjacent to the intermediate transfer belt 22 at a predetermined timing. The full-color image on 22 is secondarily transferred onto the recording paper. The recording paper on which the toner image is secondarily transferred is conveyed to the fixing unit 18. Residual toner or the like adhering to the surface of the intermediate transfer belt 22 is removed by the belt cleaning device 24.

  The recording paper conveyed to the fixing unit 18 is heated and pressurized to fix the toner image on the surface of the recording paper, thereby forming a predetermined full color image. The recording paper on which the full-color image is formed is guided to the end portion of the recording paper transport path 16 and is discharged onto the discharge tray 12a that also serves as the upper surface of the printer body 12 by the discharge roller pair 30b.

3. Characteristics of the photosensitive layer of the photosensitive drum 20 Hereinafter, characteristics of the photosensitive layer 20b, which is a characteristic part of the photosensitive drum 20 of the present embodiment, will be described. In the photosensitive drum 20 of the present embodiment, a number of elongated convex portions 60 (see FIGS. 3 and 4) extending in the axial direction of the raw tube 20a are formed on the surface of the photosensitive layer 20b in the initial use. Further, when the average intervals Sm of the convex portions 60 in the circumferential direction (rotation direction) and the axial direction (longitudinal direction) of the photosensitive drum 20 are Sm1 and Sm2, respectively, Sm1 <Sm2 is satisfied. The surface state may be at least in the initial use of the photosensitive drum 20 (the state at the start of use, in other words, the state after shipment from the factory). The average interval Sm is measured by a surface roughness measuring method defined in 1994 edition of JIS B0601 using a stylus type two-dimensional roughness measuring instrument.

(1) The average interval Sm of the irregularities
3 and 4 are schematic views showing ridge lines when the surface of the photosensitive layer 20b of the photosensitive drum 20 of the present embodiment is viewed from the axial direction and the circumferential direction, respectively. FIG. 5 is a conceptual diagram showing an actual contact portion between the photosensitive drum 20 and the cleaning blade 52 of the present embodiment where Sm1 <Sm2. FIG. 6 is a conceptual diagram showing a contact portion between the conventional photosensitive drum 20 and the cleaning blade 52 where Sm1 = Sm2.

  When the contact portion between the photosensitive drum 20 and the cleaning blade 52 is observed from the pressure contact direction of the cleaning blade 52 (the right direction in FIG. 2), when Sm1 <Sm2, the actual contact portion R1 has an elliptical shape as shown in FIG. . At this time, the minor axis of the ellipse is the circumferential direction (arrow AA ′ direction) of the photosensitive drum 20, and the major axis of the ellipse is the axial direction of the photosensitive drum 20 (arrow BB ′ direction). On the other hand, when Sm1 = Sm2, the actual contact portion R2 is circular as shown in FIG. A description will be given of whether the difference in the shape of the contact portion causes a difference in the slipping property of the external additive.

  First, the mechanism of slipping of the external additive will be described. FIG. 7 is a schematic diagram showing a state in which the external additive G stays at the contact portion between the photosensitive drum 20 and the cleaning blade 52. As shown in FIG. 7, the external additive G stays on the upstream side of the edge portion of the cleaning blade 52 with respect to the rotation direction of the photosensitive drum 20 (the arrow direction in FIG. 7). It is expected that the amount of slippage of the external additive G increases as the average distance (gap) between the photosensitive drum 20 and the cleaning blade 52 increases.

  The cleaning blade 52 is elastically deformable, and deforms following the uneven shape when the unevenness of the surface of the photosensitive layer 20b of the photosensitive drum 20 is small. However, as the unevenness on the surface of the photosensitive layer 20b increases (the arithmetic average roughness Ra increases), the cleaning blade 52 cannot follow the uneven valley portion, and a gap is generated between the cleaning blade 52 and the photosensitive drum 20. Cheap. The larger the gap is, the more external additive enters the gap, and the external additive tends to slip through the cleaning blade 52. Further, the probability that the external additive slips through increases as the gap widens with the stick-slip motion of the cleaning blade 52.

  In the case of the conventional photosensitive drum 20 in which Sm1 = Sm2, as shown in FIG. 6, the axial direction (arrow BB ′ direction) of the photosensitive drum 20 is in contact with the circumferential direction (arrow AA ′ direction). Since there is a region (region surrounded by a broken line in FIG. 6) where the portion without the portion R2 (convex portion 60) continues, the amount of the external additive passing through this region relatively increases. As a result, the charging roller 42 is contaminated and the cleaning performance is deteriorated by the cleaning blade 52, and the image is easily affected.

  On the other hand, in the case of the photosensitive drum 20 of the present embodiment in which Sm1 <Sm2, as shown in FIG. 5, the circumferential direction (arrow AA ′) in any part of the photosensitive drum 20 in the axial direction (arrow BB ′ direction). Since the contact portion R1 (convex portion 60) always exists as viewed in the direction), there is no portion where the amount of slipping through of the external additive is relatively large. As a result, contamination of the charging roller 42 and deterioration of the cleaning property by the cleaning blade 52 are less likely to occur, and the image is hardly affected. From the above, it can be said that the photosensitive drum 20 of the present embodiment in which the elongated protrusions 60 are formed in the axial direction has a more advantageous surface shape against slipping of the external additive.

  As described above, since the cleaning blade 52 is elastically deformable, it deforms so as to follow the uneven shape on the surface of the photosensitive drum 20 between large protrusions (portions). In particular, when the interval between the convex portions is wide, the contact area between the cleaning blade 52 and the photosensitive drum 20 increases. When Sm1 and Sm2 are increased, the convex portion 60 (mountain) is enlarged (the crest of the mountain is wide), and when the top portion of the convex portion 60 is worn due to long-term use, a wide flat portion is generated at the top portion, and cleaning with the photosensitive drum 20 is performed. The contact area with the blade 52 increases.

  When the contact area increases, the driving torque of the photosensitive drum 20 increases due to friction with the cleaning blade 52, and the wear of the cleaning blade 52 becomes remarkable. The slipping occurs, or the edge of the cleaning blade 52 is lost. If the edge of the cleaning blade 52 is lost, the cleaning property is deteriorated and a good image cannot be obtained.

  Therefore, it is preferable to set the average intervals Sm1 and Sm2 of the convex portions 60 as small as possible to suppress an increase in contact area due to elastic deformation of the cleaning blade 52 following the surface shape of the photosensitive drum. Specifically, the range of 1 ≦ Sm1 ≦ 10 [μm] and 10 ≦ Sm2 ≦ 20 [μm] is preferable.

(2) Arithmetic mean roughness Ra
The arithmetic average roughness Ra of the surface of the photosensitive layer 20b at the initial stage of use may be in the range of 20 [nm] to 100 [nm]. When the arithmetic average roughness Ra is smaller than 20 [nm], the friction between the cleaning blade 52 and the photosensitive drum 20 is increased, and the cleaning blade 52 is worn by long-term use, and the external additive slips through to cause image defects. The amount increases. That is, a good image cannot be obtained over a long period of time. On the other hand, when the arithmetic average roughness Ra is larger than 100 [nm], the gap between the cleaning blade 52 and the surface of the photosensitive layer 20b becomes large. For this reason, slipping of the external additive and contamination of the charging roller 26 due to the slipping of the external additive start from a relatively early stage of durable printing, and an image defect due to uneven charging on the surface of the photosensitive drum 20 occurs.

  The durability of the photosensitive drum 20 and the durability of the cleaning blade 52 vary depending on the external additive used, the photosensitive layer 20b, the material of the cleaning blade 52, and the like, but the arithmetic average roughness Ra is in the above range. It is possible to cope with various external additives, photosensitive layers 20b and cleaning blades 52 of various materials.

(3) DUH Hardness It is preferable that the DUH hardness of the photosensitive layer 20b in the initial use of the photosensitive drum 20 is in the range of 500 [kgf / mm ² ] to 1200 [kgf / mm ² ]. This is because when the DUH hardness is smaller than 500 [kgf / mm ² ], the photosensitive layer 20b of the photosensitive drum 20 is easily worn by contact with the cleaning blade 52 and the rubbing roller 53, and cannot be used for a long period of time. From this viewpoint, a higher DUH hardness is preferable. For this reason, the upper limit of the DUH hardness is defined by the hardness of the photosensitive layer 20b having the highest hardness that can be currently used. The DUH hardness refers to an indentation hardness (Martens hardness) measured by a dynamic ultra-micro hardness meter (DUH series, manufactured by Shimadzu Corporation).

(4) Area It is preferable that the average intervals Sm1 and Sm2 and the arithmetic average roughness Ra are in the above ranges in the entire image forming area on the surface of the photosensitive drum 20.

(5) Toner External Additive Titanium oxide or silica, which is conductive abrasive fine particles, is externally added to the toner as an external additive. If the arithmetic average roughness Ra on the surface of the photosensitive layer 20b is large, the cleaning blade 52 is used. The external additive slips through the uneven gap that cannot follow. Therefore, it is preferable that the external additive of the toner used for the photosensitive drum 20 of the present embodiment has a primary average particle diameter of 10 nm or more.

(6) Method for forming irregularities Regarding the method for forming irregularities, for example, a male mold that causes a trace depression is disposed on an aluminum tube 20a, and a pressure plate is pressed to obtain a desired surface shape. Thereafter, a method of forming an amorphous silicon photosensitive layer 20b on the outer peripheral surface of the raw tube 20a, or by rotating the raw tube 20a while reciprocating the cutting tool (cutting tool) in the axial direction in the cutting tool, the outer periphery of the raw tube 20a An example is a method of forming a photosensitive layer 20b of amorphous silicon after forming a bite on the surface. In particular, the latter can appropriately obtain a desired unevenness by adjusting the moving speed of the cutting tool and the rotational speed of the raw tube 20a.

  FIG. 8 is a conceptual diagram showing how irregularities are created in the raw tube 20a by cutting, and FIG. 9 is a diagram showing a locus when the cutting tool 70 reciprocates once on the raw tube 20a in FIG. In addition, in FIG. 9, it has shown as the top view which expand | deployed the cylindrical raw tube 20a.

  Now, the rotational speed (linear velocity) of the tube 20a is v1, the moving speed of the cutting tool 70 is v2, the axial length of the tube 20a is L, and the radius is r. In order to satisfy Sm1 <Sm2, the inclination angle θ of the locus S of the cutting tool 70 with respect to the axial direction of the raw tube 20a may be less than 45 °. Here, since tan θ = v1 / v2, it is necessary to satisfy v1 <v2 in order to satisfy θ <45 °. That is, the cutting tool 70 is reciprocated in the axial direction of the pipe 20a while rotating the pipe 20a so that the rotational speed v1 of the pipe 20a and the moving speed v2 of the cutting tool 70 satisfy the relationship of v1 <v2. You just need to form eyes. The pitch in the circumferential direction of the unevenness can be adjusted by adjusting the inclination angle θ by changing v1 and v2.

  As described above, the photosensitive drum 20 and the image forming apparatus 11 according to the present invention have been described by way of the embodiments. However, the present invention is not limited to the above-described embodiments, and for example, the following modifications may be made. Good. In addition, examples that are not described in the above embodiment and design changes that do not depart from the gist of the present invention are also included in the present invention.

  In the above embodiment, a tandem color printer has been described as an example of the image forming apparatus 11. However, the image forming apparatus 11 can be applied to, for example, a rotary color printer or a monochrome printer. Further, the present invention can also be applied to an image forming apparatus such as a copying machine, a facsimile, or a multifunction machine having these functions. The image forming apparatus 11 may have each configuration of the color printer described in the embodiment, or may have another configuration. However, it is necessary to provide the electrophotographic photosensitive member described by taking the photosensitive drum 20 as an example. Further, it is preferable to have a cleaning blade 52 as means for cleaning the electrophotographic photosensitive member.

  The photosensitive drum 20 in the above embodiment uses the cylindrical raw tube 20a as a support, but may use a support of another shape. Other shapes may be a plate shape or an endless belt shape. In the above-described embodiment, the photosensitive drum 20 uses amorphous silicon as the photosensitive layer 20b. However, for example, the photosensitive drum 20 may include a charge injection blocking layer that blocks charge injection from the support.

  The cleaning device in the above embodiment has a structure integrally including the cleaning housing 50, the recovery spiral 51, the cleaning blade 52, the rubbing roller 53, and the like, but preferably has the cleaning blade 52. Hereinafter, the effects of the present invention will be described in more detail with reference to examples.

(1) Manufacture of Photosensitive Drum 20 Numerous bites (cutting marks) were formed on the outer peripheral surface of a mirror-finished aluminum tube 20a by the bite processing shown in FIG. The rotational speed v1 of the blank tube 20a during cutting was set to 0.5 mm / sec, and the moving speed v2 of the cutting tool was set to 1 mm / sec. Thereafter, a photosensitive layer 20b was formed of amorphous silicon on the outer peripheral surface of the raw tube 20a to produce a photosensitive drum 20 (Invention 1). The photosensitive layer 20b is formed so that the arithmetic average roughness Ra of the surface falls within the range of 4 [nm] to 60 [nm].

  When the surface roughness of the photosensitive drum 20 after the formation of the photosensitive layer 20b was measured, the arithmetic average roughness Ra was 60 [nm], and the average interval Sm1 of the unevenness in the circumferential direction of the photosensitive drum 20 was 5 [ μm], and the average interval Sm2 between the irregularities in the axial direction was 15 [μm].

Further, the DUH hardness of the surface of the photosensitive drum 20 was measured using a DUH hardness meter (DYNAMICULTRA MICRO HARDNESS TESTER DUH-201 · 202, manufactured by Shimadzu Corporation). The measurement conditions were a test depth of 150 nm, a load speed of 0.284393 mN / sec, a load range of 19.6 mN, and a holding time of 10 sec. As a result, the DUH hardness of the surface was 900 [kgf / mm ² ].

  The surface roughness is measured at a measurement length of 2.5 mm using a stylus type two-dimensional roughness measuring instrument (surfcom 1500DX, manufactured by Tokyo Seimitsu Co., Ltd.). The measurement terminal is a stylus type of 60 [°] conical diamond, and the tip radius is 2 [μm]. The measurement length is 2.5 [mm], and the cut-off value is 0.08 [mm]. The filter type is Gaussian, and the inclination correction is a least square line correction. The cut-off ratio is 300 and the measurement magnification is x100k.

(2) Comparative test The photosensitive drum 20 in which the arithmetic average roughness Ra of the unevenness and the average intervals Sm1 and Sm2 were changed by the method similar to that of the photosensitive drum 20 of the present invention 1 and the present invention 1 (present inventions 2 to 6). Comparative Examples 1 to 3 were prepared. The image forming apparatus 11 having the configuration shown in FIGS. 1 and 2 was mounted with the photosensitive drums 20 of the present inventions 2 to 6 and Comparative Examples 1 to 3, and a durability test was performed. As test conditions, a halftone image having a printing rate of 25% was continuously printed in a low-temperature and low-humidity environment (10 ° C., 10%), and the printed image was visually observed to evaluate slipping of the external additive.

  A rubber blade made of urethane rubber was used as the cleaning blade 52. As toner external additives, titanium oxide having a primary average particle diameter of 200 nm and silica having a primary average particle diameter of 20 nm were externally added to the surface of toner base particles containing a binder resin and a colorant. As a method for evaluating the slipping of the external additive, the case where the vertical streak of the image due to adhesion of the external additive to the charging roller 42 was confirmed was evaluated as x, and the case where the vertical streak was not confirmed was evaluated as ◯. In the test, continuous printing is continued up to 100,000 sheets only for the photosensitive drum 20 that is evaluated as ○ at the time of printing 50,000 sheets, and continuous printing is performed up to 500,000 sheets only for the photosensitive drum 20 that is evaluated as ○ when printing 100,000 sheets. Continued. The results are shown in Table 1 together with the arithmetic average roughness Ra and the average intervals Sm1 and Sm2.

  As is apparent from Table 1, in the photosensitive drum 20 of the first to sixth aspects of the present invention in which the average interval Sm1 in the circumferential direction of the irregularities, the Sm2 in the axial direction is Sm1 <Sm2, and the arithmetic average roughness Ra is 100 nm or less, 50,000 After the durable printing on the sheet, no vertical streak of the image due to the adhesion of the external additive to the charging roller 42 occurred. In particular, in the photosensitive drum 20 according to the first to fourth aspects of the present invention that satisfies 1 [μm] ≦ Sm1 ≦ 10 [μm], 10 [μm] ≦ Sm2 ≦ 20 [μm], an image can be printed even after the endurance printing of 100,000 sheets. In the first to third aspects of the present invention in which no vertical stripes occur and the arithmetic average roughness Ra is 20 nm or more and 100 nm or less, no vertical stripes in the image occurred even after 500,000 durable prints.

  In the present invention 5, Sm2 = 22 μm, in the present invention 6, Sm1 = 15 and the average interval of the unevenness is large, the unevenness becomes gentle, and the cleaning blade 52 follows and curves so that stick slip easily occurs. It is considered that the external additive slipping from the blade wear part occurred in the judgment after printing 100,000 sheets. Further, in the present invention 4, since Ra is as small as 10 nm, the smoothing of the photosensitive layer 20b is likely to proceed, and it is considered that the external additive slipping out from the blade wear part occurred in the determination after printing 500,000 sheets. Therefore, in order to extend the life of the photosensitive drum 20, 1 [μm] ≦ Sm1 ≦ 10 [μm], 10 [μm] ≦ Sm2 ≦ 20 [μm] is satisfied, and Ra in the initial use is set to 20 nm or more. It is preferable to do.

  On the other hand, in the photosensitive drums 20 of Comparative Examples 1 to 3, vertical stripes of the image occurred after 50,000 sheets of durable printing. The reason for this is that in the photosensitive drum 20 of Comparative Example 1 where Ra is 110 nm, the unevenness of the photosensitive layer in the initial stage of use is too large, so that the external additive slips out from the uneven portion of the photosensitive layer 20b. This is considered to be because the charging roller 42 is contaminated by the agent and uneven charging occurs. Further, in the photosensitive drum 20 of the comparative example 2 in which Sm1> Sm2 and the photosensitive drum 20 of the comparative example 3 in which Sm1 = Sm2, the region having no irregularities in the circumferential direction of the photosensitive drum 20 as shown in FIG. This is considered to be because the external additive slips through this region. From the above, it was confirmed that the photosensitive drum 20 of the present invention can suppress slipping of the external additive over a long period of time as compared with the comparative example.

  The present invention can be used for an electrophotographic photosensitive member on which a toner image is formed. By utilizing the present invention, it is possible to provide an electrophotographic photosensitive member capable of suppressing image defects over a long period of time and an image forming apparatus including the same.

11 Image forming apparatus 20 Photosensitive drum (electrophotographic photosensitive member)
20a Element tube (support)
20b Photosensitive layer 52 Cleaning blade 60 Projection

Claims (7)

A tubular support;
A photosensitive layer formed on the outer peripheral surface of the support,
A number of elongated protrusions extending in the axial direction of the support are formed on the surface of the photosensitive layer in the initial stage of use,
Ra ≦ 100 [nm], where Ra is the arithmetic average roughness of the surface of the photosensitive layer in the initial stage of use, and Sm1 and Sm2 are the average intervals between the irregularities of the surface of the photosensitive layer in the circumferential direction and the axial direction of the support, respectively. An electrophotographic photosensitive member satisfying Sm1 <Sm2.   2. The electrophotographic photosensitive member according to claim 1, wherein the Sm1 satisfies 1 [μm] ≦ Sm1 ≦ 10 [μm], and the Sm2 satisfies 10 [μm] ≦ Sm2 ≦ 20 [μm]. .   The electrophotographic photosensitive member according to claim 1, wherein the Ra satisfies Ra ≧ 20 [nm]. The electrophotographic photosensitive member according to any one of claims 1 to 3 DUH hardness of the photosensitive layer surface is characterized in that it is in the 500 kgf / mm ² or more 1200 kgf / mm ² or less.   The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is made of amorphous silicon. An electrophotographic photosensitive member according to any one of claims 1 to 5,
A cleaning member disposed to contact the surface of the electrophotographic photosensitive member and cleaning the surface of the electrophotographic photosensitive member;
An image forming apparatus comprising: A developing device for supplying toner to the electrophotographic photosensitive member;
The toner includes toner base particles containing a binder resin and a colorant, and an external additive attached to the surface of the toner base particles.
The image forming apparatus according to claim 6, wherein a primary average particle diameter of the external additive is 10 nm or more.

Images